rayon

rayon, synthetic fibers made from cellulose or textiles woven from such fibers more rayon is manufactured than any other synthetic fiber. The name was adopted (1924), in preference to artificial silk, by the U.S. Dept. of Commerce and various commercial associations. As early as 1665 the English naturalist Robert Hooke had suggested the possibility of making artificial silk, but the first artificial textile fiber was produced in 1884 by a French scientist, Hilaire de Chardonnet, and was manufactured by him in 1889. Unpopular at first because it was too lustrous and laundered poorly, it has been steadily improved. Cellulose, originally from cotton linters but now chiefly from wood pulp, washed, bleached, and pressed into sheets, is dissolved by chemicals, then forced under pressure through minute holes in a metal cap (spinneret), emerging as filaments that unite to form one continuous strand solidified by passage through a suitable liquid or warm air. The spinning solution may be forced through a larger orifice or slit to produce a monofilament, a ribbon, or a sheet. Filaments are doubled and twisted into smooth, silklike yarns or cut into staple lengths and spun. Spun rayon can be treated to simulate wool, linen, or cotton. There are four methods of manufacturing rayon, using different materials and processes. In the nitrocellulose process developed by Chardonnet, no longer of commercial importance, cellulose is treated with nitric and sulfuric acids. In the viscose process discovered in 1892, it is treated with carbon disulfide, then dissolved in caustic soda, forced through a spinneret, and hardened in sulfuric acid. Viscose rayon is the most important type commercially, being used in most kinds of wearing apparel, furniture fabric, and carpets. For cuprammonium rayon, the cellulose is dissolved in copper oxide and ammonia, forced through holes larger than the intended diameter, then, by a process known as stretch spinning, is elongated and twisted under tension to yield a very fine, strong yarn used for sheer fabrics and hosiery. Rayon produced by these three methods is classified as regenerated, since the final product, like the original material, is cellulose. The fourth type, saponified acetate rayon, originated in England in 1918, is an acetate derivative of cellulose made by steeping cellulose in acetic acid, then treating it with acetic anhydride. Acetate rayon is more resistant to stains and creasing, is plasticized by heat, and requires special dyes, thus allowing two-tone effects with a single dye when acetate is combined with other fibers. An acetate filler is used to make shatterproof glass.